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Listeria monocytogenes infections: laboratory investigation of an unexpected increase in incidence
1Division of Infectious Diseases, Mount Sinai Hospital, New York, NY 10029-6574, USA.
Abstract:
Listeria monocytogenes is a facultative intracellular pathogen causing mainly meningitis and septicemia in immunocompromised hosts. From July 1988 through December 1989, 16 patients at The Mount Sinai Hospital were diagnosed as having listeriosis shortly after admission, 14 within a one-year period (July 1988-July 1989). Because this incidence was almost double the incidence in previous years (< 8 annually), an epidemiologic and microbiologic investigation was undertaken to determine a potential route of acquisition of L. monocytogenes. On the basis of plasmid profile, bacteriocin (enterocin) susceptibility pattern, and serotype, no single epidemic strain could be identified. Although direct evidence was lacking, we concluded that our patients may have acquired L. monocytogenes through transient contamination of food.
Insights
This study investigated a rise in Listeria monocytogenes infections at Mount Sinai Hospital. Researchers found no single epidemic strain, suggesting food contamination as a likely source of listeriosis.
Area of Science:
- Infectious Diseases
- Epidemiology
- Microbiology
Background:
- Listeria monocytogenes is a pathogen causing meningitis and septicemia, particularly in immunocompromised individuals.
- A significant increase in listeriosis cases was observed at The Mount Sinai Hospital between July 1988 and December 1989.
- The incidence rate nearly doubled previous annual rates, prompting an investigation into the source of infection.
Purpose of the Study:
- To investigate the cause of increased listeriosis cases at The Mount Sinai Hospital.
- To identify the potential route of acquisition for Listeria monocytogenes in hospitalized patients.
Main Methods:
- Epidemiologic and microbiologic investigation of 16 listeriosis cases.
- Analysis of bacterial isolates using plasmid profiling.
- Assessment of bacteriocin (enterocin) susceptibility patterns.
- Serotyping of Listeria monocytogenes strains.
Main Results:
- No single epidemic strain of Listeria monocytogenes was identified among the patient isolates.
- The investigation did not pinpoint a specific common source or outbreak strain.
- The observed increase in cases occurred over a concentrated period.
Conclusions:
- Despite the lack of a definitive epidemic strain, transient food contamination is hypothesized as the probable source of L. monocytogenes acquisition.
- Further research may be needed to confirm foodborne transmission routes in hospital settings.